1. Field of Use
This invention relates generally to hydraulic control systems employing flow control valves. In particular, it relates to cam operated flow control valves which are responsive to a system condition to effect control of a hydraulic component in the system.
2. Description of the Prior Art
Some conveyor systems, for example, comprise a conveyor drivable at variable speeds by a hydraulic motor which is controlled by a flow control valve. Sensing means responsive to some condition on the conveyor requiring a change in speed (i.e., excessive accumulation of conveyed articles requiring conveyor slow-down) are connected to the flow control valve to effect a corresponding change in conveyor speed. Such a prior art flow control valve typically embodies a valve stem which is connected to a lever in the sensing means which rotates the stem to enable the rate of fluid flow through the valve to be established at any flow rate between zero gallons per minute (gpm) and the maximum flow rate of which the valve is capable. However, since the valve stem is operating directly against relatively high fluid pressure in the system (on the order of 1000psi, for example), the sensing means lever needs to exert great force to operate the valve. Furthermore, because of high system pressure, leakage occurs around the rotatable valve stem and sealing is a problem.